zredbaron Posted November 25, 2008 Share Posted November 25, 2008 scott, again, thank you for your reply. i obviously am not content with my lack of success, and welcome [ie could benifit from] experience in the subject. i am self taught, and have never met a so-called carb guru. no doubt they do exist, but my experience is that those that i *have* been referred to [those that have been described as masters or gurus], were in fact nothing of the sort. they were merely the only person around that could get a decent tune. in my experience, i knew more about what my car needed than they did. after years of experimentation and reading, i too can get a decent tune. the difference is, i know where i fall short. where am i going with all this? even i don't know! haha. no, seriously... i agree with you that you can have pretty much the same a/f graph with different e-tube and main/air combos. i saw it this past weekend. i do however respectfully completely disagree with your pump jet comments, both in theory and in practice. in theory, the pump jet is mechanical, not hydro-pneumatic, and provides a squirt powered by the thrusting of your foot. it's a split second worth of fuel, and as such cannot possibly effect an a/f *graph* (ie rpm range). in practice, the same pump jet has been in every stage of my car's evolution, from stock 2.4L to street 3.1L to full race engine. in every stage, the car has always had instantaneous throttle response, which i credit to both the torque transfer of our L6s and the capability of the pump circuit. i see no need to change the pump jet. the car falls in its face when you maintain full pedal, NOT when you transition to it. in fact, as the pedal is depressed, the car lurches forward. then promptly chokes for air. you might be right about floats. i haven't looked at mine in years, and its certainly worth looking into again. i find it unlikely to be a fuel supply problem, as i have a high flow/low pressure centrifugal pump that can outflow any realistically possible burn rate. float level controls the depth of fuel in the float bowl and therefore the point at which the main circuit starts. a low fuel level restricts main circuit startup; too high a level can overrun the well and dump raw fuel into the throttle bore. [later in the book:] ...it affects the point at which the main circuit starts and affects the operation of the emulsion tube. it describes the adjustment, and doesn't offer it as a tuning aid, but rather for us to set it to precise measurements and does not mention application. i suppose we should all verify these adjustments... -mark ps - want some webers again, do you? funny... i'm finally considering ITBs... Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 25, 2008 Share Posted November 25, 2008 IMO, The Webers are indeed an all-out race carby. The lack of a low-vacuum enrichment circuit on the DCOE Webers is their Achillies' Heel for streetability. That workaround can bandaid so many situations where the Webers want to fall flat on their face. This is especially true for the larger choke sizes and relatively low velocity, highly pulsed airflow through the venturis. You have to keep in mind that each "barrel" of a DCOE sees a single pulse every other revolution. This means that airflow is not even close to smooth flowing. Quote Link to comment Share on other sites More sharing options...
zredbaron Posted November 25, 2008 Share Posted November 25, 2008 unfortunately what i stated earlier about one float measurement fits all is incorrect. under the dcoe chapter, there is a table with columns for multiple parts of the float measurments. it offers production car settings for alfa romeos, lotus, lamborghinis, aston martins, maseratis, bmws, but no datsun L6s. back to the drawing board. pick one? try another and note the difference? i'm tired of this shot-in-the-dark game. IMO' date=' The Webers are indeed an all-out race carby. The lack of a low-vacuum enrichment circuit on the DCOE Webers is their Achillies' Heel for streetability. That workaround can bandaid so many situations where the Webers want to fall flat on their face. This is especially true for the larger choke sizes and relatively low velocity, highly pulsed airflow through the venturis.[/quote'] agreed, furthering my inclination toward ITBs. the nostalgia factor and purist side of me are screaming NO..., but damnit jim, i want a GOOD tune (and therefore a more useable power band!) by no means am i giving up, and will continue to post any findings (or lack of them)... i'm merely conceding that it looks like 'tuning' webers is more like 'getting them to run well in *part* of the power band.' [more so for modded cars than stock cars. my old stock L24 ran just fine on webers!] Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted November 25, 2008 Share Posted November 25, 2008 Don't give up Webers! I did and I miss them dearly. I had them on my Alfa Romeo and still hope to build a Tripple L24 some day. Your problem is that you are measuring AFR's! Webers are more of a seat of the pants kind of thing. (tongue in cheek). Keep up the great research! I will need this info someday. Webers "talked" to me. Fuel injection doesn't. Quote Link to comment Share on other sites More sharing options...
Daeron Posted November 25, 2008 Share Posted November 25, 2008 Don't give up Webers! I did and I miss them dearly. I had them on my Alfa Romeo and still hope to build a Tripple L24 some day. Your problem is that you are measuring AFR's! Webers are more of a seat of the pants kind of thing. (tongue in cheek). Keep up the great research! I will need this info someday. Webers "talked" to me. Fuel injection doesn't. You need to speak the right language!!! 010011011101011010101!!!! aahahahaha!!!! sorry. What about modding some Mikuni/Solexes to use weber jets so you get the tunability of the weber jetting selection, but the drivability of the solexes.. (solexes have this low vacuum enrich circuit, don't they? I am teaching myself about carbs finally and know there was a drivability reason my uncle tended towards solexes in his roadsters and his Z rather than webers..) In my mind I've always put the Mikuni before the weber simply because it was a factory option on the roadsters.... but at the same time I have long since adapted the common lingo of just calling them all "triple webers." TBH, I've really got next to no idea what the detailed differences between them are.. to the Google Cave!!! Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted November 25, 2008 Share Posted November 25, 2008 zredbaron. Actually the pump jet continues to deliver fuel throughout the RPM range when at WOT. It gives that initial shot of raw fuel, but fuel is still pulled through that jet during WOT. As for the float settings, it depends on the type of float you have. I have measurements that I use with 40 and 45 dcoe's that use the brass floats. If I recall it should be set at 7 and 15mm (closed and open). It is kind of difficult to put in words, but you measure with the carb lid gasket in place, and measure from the gasket to the smooth part of the float, not the soldered seam, and you measure from the point at which it starts to touch the needle valve, and point at which the float is at full "droop" for lack of a better word. Scott. Quote Link to comment Share on other sites More sharing options...
Lazeum Posted November 25, 2008 Share Posted November 25, 2008 Scott- How do you setup the float height? Do you bend something? I've seen many picture showing how to measure but nothing to know to chnage settings... Quote Link to comment Share on other sites More sharing options...
zredbaron Posted November 25, 2008 Share Posted November 25, 2008 Actually the pump jet continues to deliver fuel throughout the RPM range when at WOT. It gives that initial shot of raw fuel, but fuel is still pulled through that jet during WOT. well if this is true, then that's news for me. i'm merely going off the weber book, and the weber book does NOT mention that. The extra dose is provided by the accellerator pump' date=' which squirts a shot of raw gasoline into the intake manifold when the throttle is opened. On a DCOE carburetor, the accellerator pump is literally a pump: a piston in a cylinder. The piston is operated by a cam and linkage off the throttle shaft. [/quote'] this page has a few diagrams that the weber book does not have, in addition to a few that are already depicted in the weber book. unlike the weber book, however, it explains the diagrams and identifies the parts of the carb shown: http://www.teglerizer.com/dcoe/rasorcom.htm i still don't get the impression that fuel is ever 'drawn' through the accelerator circuit, but hey, does it really matter? i really don't think this jet is making or breaking any significant portion of the rpm range. i suppose i could test this theory by removing the jets completely and seeing if WOT is any different... with regard to float settings: matt, don't even think about adjusting floats without studying diagrams. there are a couple provided on the link above. it mentions the numbers 8.5 and 15.0. (reference the diagrams to see what these numbers mean). yes, you adjust the float be bending a tab that touches the check ball. there is also another tab that limits the float drop, and this is the tab that doesnt touch the ball. both tabs pivot around the same pin. pull it out and compare the real thing to the diagrams and you should be able to get it. in fact, 2/3 of the cars listed in the weber book want the floats at 8.5 and 15.0. a few are at 7.0 and 13.5, and there are a few odd ball applications that vary from there. again, no true equivalent to the L6 is listed. i wish i knew what raising or lowering each measurement would do (which one delays when the main circuit kicks in? which one affects the emulsion tube? how/why?) Quote Link to comment Share on other sites More sharing options...
Lazeum Posted November 25, 2008 Share Posted November 25, 2008 Mark, on the following link, They seem to believe float level is having a big impact on when the main circuit starts to act and it can improves our rich spot. However, it is happening at 4500rpm; way after the mains start to pour gas so I'm a little confused. The interesting thing, the spot happens with my setup (L28, 32mm choke), Mark's setup (L31, big choke) and Innovate forum OP (1600cc honda engine, 45DCOE and 38mm choke). So we can eliminate choke size, DCOE type, air/main jets since our setups are all different regarding those items. It seems the spot is not related with the emulsion tubes. It seems weird to me since they are the features that control behavior of the richness over the rpm range. I'm not completely sure to understand in detail how emulsion tube works. I do understand the slowing process with air bubble but does the level of fuel into the emulsion tube chamber change with vacuum? Should we try an emulsion tube with different type of holes in the middle of the tube then since our rich spot happens in the middle of the rpm range? I would have to look at emulsion tubes blue prints to check richness difference vs. tube design. They put salt on the roads today I might have to wait before to do any test but I would think I can give a try with the wideband to see the impact of float level (with 1mm change for instance). Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 25, 2008 Share Posted November 25, 2008 Ahhh.. Emulsion tube.... A problem inherent in all Carbys is slow response time. One of the ways they improve the response to rapidly changing conditions is to "lighten the fluid" in the passages. They do this by mixing the fuel with air-bubbles. This is where the emulsion tube comes into play. The shape and placement of the air passages in the E-tube serves to mix the bubbles with the fuel in the well. The emulsion well ensures that there is plenty of extra fuel available to the E-tubes when instant demand sucks fuel out of the well faster than the main jets are replenishing it. The heavy fuel in the main jets is slower to begin flow and the inertia of the heavy fuel keeps it flowing a little too long. The E-tube and it's well act as buffers in the system and greatly improve the response time. About the plethora of E-tube designs: The various E-tube designs were intended to work around issues with various carby applications. A quick revving race motor has entirely different requirements than a slower reving street engine. The positions of the air holes are also intended to work with specific float levels. You really need to figure out which application the various E-tubes were made for and then look up the float levels and jetting that particular E-tube was designed for. As an example: one of the designs I have seen has passages drilled at angles. I figure that the passages were intended to maintain constant flow even when the well was nearly emptied. This would make sense on a race motor where the engine can rev very quickly. A lot of fuel may empty from the well before the main jets begin to flow enough to replenish it. The angled passages help to "lift" the fuel into the rest of the system. Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 25, 2008 Share Posted November 25, 2008 The Accelerator pump design for the Webers is unique. The Pump piston is mechanically raised whenever the throttle is closed. Fuel is drawn into the cylinder and the pump is ready for operation. When the throttle is opened the piston is actually driven down by a spring(not the throttle arm). This allows the duration and volume of the extra fuel to be controlled by changable jets. The system has 2 check valves. Both check valves ensure that a full charge of fuel can be drawn into the cylinder as quickly as the throttle shaft closes(very quickly). The upper check vavle(21) ensures that fuel is drawn from the bowl not the delivery passages. The lower check valve(23) allows fuel to fill the cylinder at a high flow rate. This lower check vavle also houses a bleed hole that will allow some fuel to be(slowly) returned to the bowl. The amount of fuel delivered and the duration of the charge can be altered by changing the delivery jet size and the return(bleed hole) back to the bowl. I think there may be alternate springs as well. To answer the idea that fuel is drawn from the accelerator circuit all of the time; This is NOT true. The accelerator circuit has a weighted check valve(21 the wedge shaped piece above the ball) that will not allow venturi vacuum to draw fuel through the accelerator circuit. Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 25, 2008 Share Posted November 25, 2008 There are more differences in the designs of the DCOE 40s and the DCOE 45s than meet the eye(or micrometer). The design of the downward sloping passages from the main well to the venturis varies. The passages are not just round holes drilled to move fuel from one place to another. They are flattened, wide ducts that are carefully designed to keep the AIR/Fuel emulsion homogeneous on it's journey from the main well to the venturi. These ducts changed over the years and I recall reading somewhere that the ducts in the DCOE 45s were specifically sized to flow larger amounts of fuel. The lower fuel requirements of a smaller/low performance engine may be way outside of the operating conditions this larger duct was designed for. This means that the fuel/air emulsion may separate and come out of the venturi in spurts and drips instead of a nice even spray. To sum up, using a race carby on your street engine may be doing more harm than good. Using the correct carby for your application(along with venturi size) will ensure correct operation and easy tuning. Quote Link to comment Share on other sites More sharing options...
zredbaron Posted November 25, 2008 Share Posted November 25, 2008 really? now the pump circuit is adjustable beyond the jet? different springs!? now we're *really* getting in the weeds... although i don't have salt roads here in VA and am still 'able' to drive, the concrete is cold enough that i can't put the power down unless i trailer the car to an open road somewhere and do it at higher speed (i prefer carb tuning in 2nd/3rd; 2nd breaks loose at about 5000 and 3rd would be unsafe locally) (2nd holds in the summer). so yeah, i might have to wait till next summer, too. the navy has plans for me to deploy to the middle east soon, anyway. i've been reading that honda thread, and they stress the importance of float levels, too. i find this promising. i still suspect an F9 (similar to F11 but leaner) would be good even after making sure the floats are right. some highlights from the other site's weber thread: 8.5 mm is typical for brass floats and 12.5 mm is typical for plastic floats it occurred to me that the float's mass makes a difference' date=' and sure enough I started measuring and have found significant differences in masses of floats, which means they'd be giving different fuel levels for the same float level! That's why I started measuring the fuel level instead of the float level. You stated that the car runs great but it's pig rich (10-11.5A/F) from 3000-4500. Well, that's the area most affected by float level! If the fuel level is too high, the main circuit comes on too early (and too hard), since the fuel barely has to climb up any to reach spillover out the aux venturi. Dropping the float level will delay this tip-in. [/quote'] who knows, the float levels just might do the trick! there are some promising directions to go at the very least. Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 25, 2008 Share Posted November 25, 2008 really? now the pump circuit is adjustable beyond the jet? different springs!? now we're *really* getting in the weeds... Yes. There are several parts that alter the duration and volume the accelerator pump delivers. The pump jet(23?) you refer to only adjusts the bypass flow returning to the float bowl. The ball-check valve is not a metering orifice, it is a full-flow orifice. The only metering part of that jet(23) is the return/bypass orifice. The pump exhaust jet is under a brass cap with a flat-head screw slot. This is yet another piece that is used to change the performance of the acc-pump circuit. I have personally found that the springs vary from model to model. I believe these are also an available tuning part, though I have not found a part number to order a different set of springs. Quote Link to comment Share on other sites More sharing options...
zredbaron Posted November 25, 2008 Share Posted November 25, 2008 really? now the pump circuit is adjustable beyond the jet? different springs!? now we're *really* getting in the weeds... Yes. There are several parts that alter the duration and volume the accelerator pump delivers. I have personally found that the springs vary from model to model. I believe these are also an available tuning part' date=' though I have not found a part number to order a different set of springs.[/quote'] ...really? i was being sarcastic. sorry. i personally would prefer to keep the focus of the thread on fixing big picture issues [flat spot!] vice polishing areas that probably aren't even noticeable. but hey, that's me. i'm a crazy man, and i don't own the thread... Quote Link to comment Share on other sites More sharing options...
Zmanco Posted November 25, 2008 Share Posted November 25, 2008 When I had triples I did play around one afternoon with float levels and could not find any significant repeatable changes from small adjustments. I was using a narrow band O2 sensor and 2nd and 3rd gear pulls on an empty road so it was anything but scientific. But I suspect that tweaking float levels is not going to solve the flat spot issue unless the float levels are currently way out of spec. Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 26, 2008 Share Posted November 26, 2008 Z-red Baron. Sarcasm has no place here. If you had the opportunity to open up a few more Webers you would quickly find out that there are hundreds of differences that are not on the list of tuning parts in your catalog. This is one of the main reasons for aquiring a set of Webers that have closely matched serial numbers. On top of that, MANY MANY MANY racers have further modified their carbys well beyond what has been discussed here. You guys do realize that you can check float levels for consitency with a depth guage with the jet cover removed. That won't directly relate to the float adjustment measurements given in the manual. But you can make checks for changes and calibrate the carbys together using the depth gauge. I media blasted the extension on my gauge so the fuel would wet the surface and make it easier to read. There are many other things that you guys have not mentioned that I consider important to getting Webers to work properly. Such as setting the throttle stops. The throttle stop position IS NOT AN IDLE ADJUSTMENT. It should be set the SAME for every carby in the system. The throttle stop position is set in relation to the positions of the transfer holes. The idle mixture screw is how you adjust idle air flow(fuel is metered by the idle jet in the bowl). The idle port and the transition holes work together to act as an Idle emulsion circuit. This plays into another important area of Weber tuning, Transition holes. This is also another area that will make carbys vary GREATLY in their Idle jetting requirements. Transition holes are another area that differs from one DCOE to another. The pattern, number, and size of the transition holes changed GREATLY from one application to the next. Many carbys have had bypass holes drilled in the throttle plates. Others have had the transition holes slotted and grooves engraved in the throttle bores. All of these things can conspire against you to create problems with off-idle operation. Keep in mind that getting a good idle with the throttle plates in the wrong stop-position means you have attained the wrong idle/transition mixture settings. The entire transition circuit will be out of whack and create drivability problems. Just because you can get it to idle smoothly does not mean that it is idling correctly. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted November 26, 2008 Share Posted November 26, 2008 I have a very nice diagram in one of my manuals that illustrate the accel pump jet, and it specifically notes that fuel is pulled through at full throttle. I don't have hard numbers to say how much it affects your fuel ratio, but it definately needs to be considered when selecting your air correctors. As for differences in carbs, there are 10 known variations of of the 45DCOE9. There is no guide for which carb designation means what, as it appears it was random, and depended on the application for the carb. As long each of your carbs have the same codes on them, consider yourself lucky and leave it at that. I have never seen a comprehensive list of what model carb goes with what application, and details of all of the differences. I don't think anyone knows. The same goes for Emulsion tubes. That is why most people do not bother with testing with them. too many variables that would take lots of time and $ to test with. As for the F16 tube, it causes the main circuit to start earlier than the F4-F15 etubes. The angled holes help rather than retard fuel flow unlike some of the older e tube designs. Emulsion tubes do not make a mixture rich or lean. They only change the rpm range, and the rate (speed for lack of a better word) in which it affects the main circuit. Dropping in an emulsion tube is not going to simply "fix' your tune. You will likely need to make other jetting changes. For floats, I would not recommend using float settings to adjust your mixtures. If so, you are really on your own for tuning information. I agree with bjhines that there are many other aspects not talked about much around the mechanical state/tune of your carbs. I'm not sure I could explain in an understandable way details on how/what to check, and how to adjust them. I'm not trying to scare people away from webers ( or any multiple carb setup) It just makes troubleshooting much more precise, and it is what is required to get more than just a "good' tune. It took me a lot of time and serious money to get my carbs setup. I read every word in my manuals a half dozen times before I even took my carbs out of the box. I spent hours examining and mechanically setting up the carbs before I installed them on the car. I talked with alot of weber owners in my Z club, I offered my time for free to work in my mechanics shop and learn all his tips and tricks with building, installing, and tuning webers. This really got me interested, and I spent waayyy toooo much buying any weber stuff I could find at swaps and auctions to build a collection of everything I could ever need for my carbs. All my tuning experience grew from a hobby to an obsession. Quote Link to comment Share on other sites More sharing options...
bjhines Posted November 26, 2008 Share Posted November 26, 2008 Well.... You know how it goes with Webers. I can't disagree with you entirely about the accel pump. The accel pump has a weighted check valve. Obviously the "check" portion of the valve will allow fuel to freely flow, but the weight is supposed to stop it unless the pump pushes hard enough. But it is certainly possible some circumstances will overcome the weight and allow it to flow. You would need some serious downstream vacuum @ WOT. ???caused by extremely small venturis at high RPM??? Quote Link to comment Share on other sites More sharing options...
Dtsnlvrs Posted November 29, 2008 Share Posted November 29, 2008 The one thing nobody has mentioned is the Needle valve size. Even my "almost" perfectly tuned trips lean out a bit (13.02 AFR) at 4500rpm-6000rpm. I am thinking of increasing the needle valve size to a 2.00 from a 1.75. Thought process goes like this....E-tube sits in a well of fuel....under WOT that well level gets lower and is filled thru the Needle Valve...the bigger the valve the faster it can be re-filled. Also...I think most of you are using WAAAAY too large a Venturi for your application...there two really good books out there http://www.dellorto.co.uk/merchandise/products_details.asp?PartNo=Powertune&CategoryID=5&PartsectionID=7 http://www.dellorto.co.uk/merchandise/products_details.asp?PartNo=9500005400&CategoryID=5&PartsectionID=7 Just my two cents....I will post my setup numbers as soon as I find my data sheet. Quote Link to comment Share on other sites More sharing options...
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